(EP323287-B)      In thermal conversion of CH4 to higher hydrocarbons in an elongated reaction zone with an axis of symmetry and comprising (a) a heating zone, and (b) a cooling zone following the heating zone and in which the effluent from the heating zone is cooled, a gaseous mixt. contg. CH4 is circulated in the heating zone in a direction parallel to the axis; the heating zone contains electric heating means, sealed from the gaseous mixt., and arranged in parallel strata, forming, in transverse projection, a bundle with triangular, square or rectangular path.    The heating means are grouped in successive transverse sections perpendicular to the axis, independent of one another and supplied with electrical energy so as to form 2 parts in the heating zone; in the 1st part, the charge can be heated to at most 1500 deg.C, and in the second part,is held at a temp. equal to the max. to which it was heated in the 1st part. A coolant fluid is fed into the cooling zone, and the higher hydrocarbon prods. are collected at the end of the reaction zone.    (DE3870198-G)      In thermal conversion of CH4 to higher hydrocarbons in an elongated reaction zone with an axis of symmetry and comprising (a) a heating zone, and (b) a cooling zone following the heating zone and in which the effulent from the heating zone is cooled, a gaseous mixt. contg. CH4 is circulated in the heating zone in a direction parallel to the axis; the heating zone contains electric heating means, sealed from the gaseous mixt., and arranged in parallel strata, forming, in transverse projection, a bundle with triangular, square or rectangular path.    The heating means are grouped in successive transverse sections perpendicular to the axis, independent of one another and supplied with electrical energy so as to form 2 parts in the heating zone; in the 1st part, the charge can be heated to at most 1500 deg.C, and in the second part,is held at a temp. equal to the max. to which it was heated in the 1st part. A coolant fluid is fed into the cooling zone, and the higher hydrocarbon prods. are collected at the end of the reaction zone.